The study of acquisition of American Sign Language in deaf children brings into sharp focus some fundamental questions about the representation of language and the representation of space. In research over the past decade, we have been specifying the ways in which the formal properties of languages are shaped by their modalities of expression, sifting properties peculiar to a particular language mode from more general properties common to all languages. The forms of syntax and discourse in a signed language are deeply influenced by the modality in which it develops, particularly in the pervasive use of spece. In the renewal grant, we focus on the interplay between the development of a spatial language and spatial cognition. 1) Longitudinal studies of spontaneous mother child interactions are interwoven with experimental investigations to chart the course of the deaf child's spatially organized syntax and discourse. 2) We contrast the development of spatially organized syntax and spatial mapping. 3) The young deaf child is faced with the dual task in sign language of spatial perception, memory, and spatial transformations on the one hand, and processing grammatical structure on the other, all in one and the same visual event; we therefore investigate the development of spatial cognition in deaf and hearing children through a battery of computerized tests. We also investigate whether acquisition of spatially organized syntax is yoked in particular ways to the development of its nonlanguage substrate (i.e., spatial cognition). 4) Language and spatial representation are attributes for which the two cerebral hemispheres in hearing individuals shows different specializations. In a series of studies, we directly examine the development of brain organization for a language in space.